The central goal of our studies is to define mechanisms controlling age- associated changes of the T cell repertoire. We have found mono and oligoclonal expansions of CD8 T cell receptor (TCR) Vbeta populations in normal elderly humans. Our preliminary results suggest that this may be the T cell equivalent of Benign B cell Monoclonal Gammopathy (BBMG). These expansions represented up to 37.5% of all CD8 cells and are probably present in almost all normal elderly subjects. RT-PCR, cloning and sequencing of the TCR beta chain VDJ junction show that these expansions are monoclonal while control CD4 subsets were polyclonal. The expanded oligoclonal subsets are CD8+ CD28- CD11b+ and lack a specific proliferative response to the relevant anti-Vbeta mAb. Our specific aims are: I) To establish the age-dependent appearance of oligoclonal CD8+ T cell populations and their TCR Vbeta distribution in healthy human subjects of different ages. This will be accomplished by screening healthy human volunteers with the panel of TCR Vbeta mAbs. 2) To directly determine the clonality of the expanded CD8+ T cell populations by sequencing both the TCR alpha and beta chains. This will be accomplished by screening subjects with the three mAbs available against the TCR alpha chain. Alternatively, TCRalpha chain genes will be cloned and sequenced from clones derived in vitro from the in vivo expanded CD8+ TCR Vbeta cell populations. 3) To determine the in vivo role of oligoclonal CD8 + T cell expansions on an active immune response. This will be accomplished by comparative analysis of the TCR Vbeta repertoire of CD8+ T cell in elderly human subjects who respond to influenza vaccination versus those who fail to respond. 4) To assess the antigenic specificity and function of the expanded CD8+ T cells. This will be accomplished by in vitro testing the antigen specific responses of lines and clones established from the in vivo expanded T cell populations; and by injection of freshly isolated CD8 + oligoclonal expansions into nude and SCID mice. The overall goal of this proposal is to confirm the clonality of these expansions and to determine their specificity and their biological significance in elderly humans.